Problems with boring on a lathe.

[kkcalvin]

Hey guys I'm fairy new to machining. I need help with boring on the lathe which I suck at probably because of crappy Harbor Freight boring bars that I use.

This is what I use

I also have two Grizzly double ended bars, one 3/8" with 1/8" tool bits and one 9/16" with 1/4" tool bits.

like this.

I tried to use the smaller one but also with crappy results. Probably because those 1/8" tool bits are pain in the but to grind + my inexperience.

I was thinking about buying these indexable boring bars from ebay:

http://www.ebay.com/itm/300352107816?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649



And maybe this for smaller holes:
http://www.ebay.com/itm/300372848585?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649



What would you guys recommend?

 

[hecirp]

Not sure what exactly you mean by poor results, but as a rule you will get better results with minimum stick out of the shank, and using the largest shank tool possible for the hole you are boring. Also the more rigid your lathe, the better the result. Try on a test piece until you are satisfied with the result, the go on to the project.
Hope that helps. Lots better to test different set ups first. Learned that from my machinist friends.
Harvey

 

[David Kirtley]

I don't know what size lathe you have but I was personally looking at the ones from Micro100.

So far though, I have the ones from LMS that came with the lathe kit and a set that came with my boring head (like yours on the left but one set 1/2 and the other 3/8) and one with the HSS like yours below the first ones.

What do I use? Usually, I just use one I ground out of 1/4 round HSS bar. It has been the sharpest and best finish. Second choice has been the brazed carbide that came from LMS. I just don't have a grinder that can touch the carbide right now so I stick to HSS mostly.

A R Warner has some really nice looking ones but they are a bit pricier. I hear good things about them. Just have not tried myself.

 

[kkcalvin]

I have Grizzly G0602, 10"x22" lathe
http://www.grizzly.com/products/10-x-22-Bench-Top-Metal-Lathe/G0602

So far I tried boring out holes ranging from .750" to 1.125" wth Harbor Freight tools both round bars and those red ones. both seem to be very dull and seem to chatter a lot if I try to use the longer ones regardless how small of a cut I take and how slow I advance.

Grizzly bar with HSS inserts I probably screw them up when grinding the inserts and somehow dull them.

Since I suck at grinding HSS inserts I'm thinking of switching to carbide. Do you guys think that those indexable boring bars are OK? Price is big factor for me.

 

[tripletap3]

I have ordered the Shars Boring Bar kit 404-2000. They have been backordered but I see it shipped today. I will let you know how it looks. Some of the stuff shars has is total garbage but I have found some very good items as well that I would put up against any brand name. Carbide on small machines can be problematic will give a poorer finish. Carbide doesn't cut like HSS, it chips the metal away that is why it needs a much faster surface speed. I use HSS anytime I can but you are limited on indexable tooling. What I am counting on is that the AR Warner HSS bits will fit these boring bars.

 

[Ray C]

The red boring bars... You'll get nowhere with them. The others... -Maybe OK if the carbides are seated and cut properly.

Boring takes a little practice and you need to get the bit centered and properly positioned just like if you were cutting normally. Are you getting good results with normal cuts? Get that down first since once you learn the basic ways of engaging the bit, you do the same thing with boring bars.

Also, unless I'm working with harder metal/alloy, I tend to use HSS when boring (but carbide most other times) because it cuts better and requires less pressure. But either way, you can't cut as deep when boring and I usually only dial-in about 1/3 to 1/2 the depth of cut (DOC) as with normal cutting. Also, after every second pass, don't dial in and make a another cut at the same setting. This will keep the cut even diameter or, if you're boring a taper, you won't get an inverted parabola.

Anyhow, boring bars are pricey for some reason despite their simplicity. Good ones are made of alloy steel or medium carbon steel and are heat treated so theywill flex less. I just have normal round bars and I modified a few to hold carbide tips. They work well enough and I can make Brown and Sharpe tapers with perfect results.

As others have noted, please describe what kind of poor results you're getting -show pics if possible and maybe we can make some suggestions.

-Nice looking lathe you got there...

Ray

 

[ScrapMetal]

Since I suck at grinding HSS inserts I'm thinking of switching to carbide. Do you guys think that those indexable boring bars are OK? Price is big factor for me.

I prefer to work with HSS for boring on this size/speed of lathe. Even though price is a big factor, you may want to take a look at the boring bars/inserts from Arthur Warner - http://www.arwarnerco.com/ as they have inserts made from HSS. They are quality tools as well.

Hope that helps,

-Ron

 

[FarFar]

Most boring problems are due to insufficient stiffnes of tool and lathe so I decided to improve both.Lathe stands rock steady on a piece of granite.
Always trying to use biggest possible boring bar.Small diameter tool block is shown on first picture.
The tool heigth is adjusted on second picture.
The small cylinder is exactly 25.14 mm long and that is distance from compound slide surface to lathe centerline

 

[FarFar]

For bigger holes I prefer an insert tool bar mounted in a homemade holder
First picture shows working situation,second shows adjusting tip heigth and last is looking inside.
The one shown in letter before is miles easier to make.

 

[FarFar]

This is total forbidden use of an innocent boring bar as milling tool in lathe four jaw chuck.
Never got round to buying a milling mashine and all my tantool holders got their rather critical clearances this way.
If You are in doubt do not try and let distance between four jaws and insert be as short as possible even if it means shortening the bar.